Intracranial pressure (ICP) is a widely monitored physiological signal for patients with various neurological / neurosurgical diseases. A wealth of pathophysiological information of cerebrospinal fluid (CSF) and cerebral blood flow (CBF) circulatory systems is embedded in ICP waveform dynamics. Nevertheless, interpretation of ICP measurement in current clinical practice, in large, considers only absolute value of ICP. Our overall goal is to develop a clinically friendly signal processing method for extracting a novel latency measure from ICP waveform and demonstrate its effectiveness as a quantitative biomarker of status of cerebral vasculature. Knowledge of cerebral vasculature status including vasoconstriction, vasodilatation, and overall vasomotor activity is important in treating and managing patients with cerebral vascular disorders and brain injury. However, direct access of cerebral vasculature in a continuous fashion is currently hindered by technical limits and by ethic considerations. Our central hypothesis is that latency of an ICP pulse relative to an extracranial circulatory timing signal is an indicator of pulse wave velocity (PWV) of blood pressure wave transmission in the cerebral vasculature. We propose two aims to study the behavioral of two ICP latency measures including the onset and the P1 latency in response to two experiment interventions: CO2 challenge and postural changes. The proposed experiment procedures will help determine the true positive and false positive aspect of using ICP latency measures for indicating cerebrovascular changes. If validated, the ICP latency measure could be useful in continuously monitoring cerebral vasculature changes that could be present in the development of cerebral vasospasm, in characterizing the reserve of cerebral vascular bed, and in quantifying the efficiency of cerebral blood flow autoregulation. PUBLIC HEALTH RELEVANCE The objectives of this project are to develop and validate a novel ICP latency measure as a surrogate of cerebrovascular changes. The ICP latency measure could be useful in continuously monitoring cerebral vasculature changes that could be present in the development of cerebral vasospasm, in characterizing the reserve of cerebral vascular bed, and in quantifying the efficiency of cerebral blood flow autoregulation.